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Re: some new user questions

On 10/26/24 09:56, void wrote:

I'm considering using tarsnap for the many machines I manage. I have a few questions not answered in the FAQ:

1. if backups happen 2-hourly and the backup/tarsnap client has been running say 3 days, is it possible to select/restore from backup taken say at the 10th hr on the 2nd day?


Every time you (successfully) create an archive, you have an archive.  You can
extract any archive you created and have not deleted.

Of course you can only extract an archive you created; if creating an archive
takes more than 2 hours then when you try to create another archive 2 hours
later it won't succeed because the first one will still be in progress.


2. if a directory has soft symlinks, will the backup traverse the symlink?
or do I need the backup to look at the full real path?


Tarsnap respects standard tar command line options:

     -H      (c mode only) Symbolic links named on the command line will be
             followed; the target of the link will be archived, not the link
             itself.

     -L      (c mode only) All symbolic links will be followed.  Normally,
             symbolic links are archived as such.  With this option, the
             target of the link will be archived instead.

The default behaviour is that symlinks are just stored as symlinks.  In
particular -L is dangerous since you can create infinite loops (e.g. if
you create a symlink /home/void/foo/bar/homedir -> /home/void) and following
such infinite loops would create an infinitely large archive.


For example, a user has an sftp-only account chrooted to his homedir and there's a link from there going to a place on a webserver they have rw access to. Is it sufficient to back up only the homedir, or do I have to back up the full web path, or does it matter?


I also recommend that new users run tarsnap with the -v flag, which prints a
list of files as they are archived, to make sure it's doing what you expect.


3. like I mentioned, there's many machines to run backups for. Can I do them all under the one account?


Yes, but (barring some exceptional and complicated configurations) you'll
need to create separate keys (using the tarsnap-keygen utility) for each
machine and they will only be able to access their own data (each "machine"
gets its own storage space).

--
Colin Percival
FreeBSD Release Engineering Lead & EC2 platform maintainer
Founder, Tarsnap | www.tarsnap.com | Online backups for the truly paranoid